HCCI heavy mixing mode

Abstract

A method for operating a multi-stroke homogeneous charge compression ignition engine is described. The method includes late intake valve opening (LIVO) and also cycling air and fuel charge from the cylinder back into the intake manifold during a compression stroke to mix the air and fuel charge for later reintroduction and combustion.

We claim: 
     
       1. A method for operating a multi-stroke homogeneous charge compression ignition engine having a plurality of cylinders using electronic valve actuation, comprising:
 actuating at least one intake valve of a cylinder with a late intake valve opening (LIVO); 
 receiving an air and fuel charge in the cylinder; 
 opening the at least one intake valve during a compression stroke of a piston in the cylinder to cycle the air and fuel charge into an intake manifold to mix the air and fuel charge; 
 opening the at least one intake valve to receive at least some of the mixed air and fuel charge from the intake manifold during an intake stroke; and 
 compressing the mixed air and fuel charge to auto-ignition to generate HCCI combustion without applying spark ignition to the mixed air and fuel charge. 
 
     
     
       2. The method of  claim 1  wherein the engine is transitioned to HCCI combustion, and wherein the LIVO is late intake valve opening from a closed position, the opening timed late with respect to top dead center, and the opening further during a later portion of downward piston movement from top dead center to bottom dead center, but before bottom dead center, and wherein the opening during the compression stroke includes opening the at least one intake valve from closed between bottom dead center and top dead center and during upward piston movement. 
     
     
       3. The method of  claim 2 , wherein transitioning the engine to HCCI combustion comprises transitioning the engine to a two-stroke HCCI combustion cycle. 
     
     
       4. The method of  claim 2 , wherein transitioning the engine to HCCI combustion comprises transitioning the engine to a four-stroke HCCI combustion cycle. 
     
     
       5. The method of  claim 1  further comprising receiving the fuel charge by direct injection after an intake valve opening event. 
     
     
       6. The method of  claim 1 , further comprising:
 retaining some of the mixed air and fuel charge in the intake manifold; and 
 opening the at least one intake valve to receive the mixed air and fuel charge from the intake manifold during the intake stroke following a first HCCI combustion. 
 
     
     
       7. The method of  claim 4 , further comprising:
 retaining some of the mixed air and fuel charge in the intake manifold; and 
 opening the at least one intake valve to receive the mixed air and fuel charge from the intake manifold during the intake stroke following a second HCCI combustion. 
 
     
     
       8. A method of operating a multi-cylinder engine with an intake and exhaust manifold, the engine having a cylinder with at least an intake and exhaust valve, the method comprising:
 operating the cylinder of the engine with at least the following successive strokes:
 a first stroke having downward piston motion where charge from the intake manifold is inducted into the cylinder and where the intake valve opens substantially after top dead center of the first stroke; 
 a second stroke having upward piston motion where the inducted charge is first compressed with both intake and exhaust valves held closed, and where the intake valve opens substantially after bottom dead center, but before top dead center of the second stroke to deliver at least some of the charge back to the intake manifold; 
 a third stroke having downward piston motion where at least some of the charge is re-inducted from the intake manifold with the intake valve remaining open from the second stroke and at least partially into the third stroke; and 
 a fourth stroke having upward piston motion where the re-inducted charge is compressed to auto-ignition with the intake and exhaust valves closed. 
 
 
     
     
       9. The method of  claim 8  further comprising:
 a fifth stroke having downward piston motion with the intake and exhaust valves closed; and 
 a sixth stroke having upward piston motion to exhaust the auto-ignited charge past the exhaust valve. 
 
     
     
       10. The method of  claim 8  further comprising injecting fuel into a port upstream of the intake valve before said first stroke. 
     
     
       11. The method of  claim 8  further comprising directly injecting fuel into the cylinder during said first stroke. 
     
     
       12. The method of  claim 8  further comprising operating the cylinder with spark ignition in a cycle immediately before the first stroke, so that the cylinder transitions combustion to four-stroke HCCI combustion immediately after the fourth stroke. 
     
     
       13. The method of  claim 9  further comprising operating the cylinder with spark ignition in a cycle immediately before the first stroke, so that the cylinder transitions combustion to four-stroke HCCI combustion immediately after the sixth stroke. 
     
     
       14. A computer storage medium having non-transitory instructions encoded therein for operating a multi-stroke homogeneous charge compression ignition engine having a plurality of cylinders using electronic valve actuation, said medium comprising:
 code to actuate at least one intake valve of a cylinder with a late intake valve opening (LIVO); 
 code to receive an air and fuel charge in the cylinder; 
 code to open the at least one intake valve during a compression stroke of a piston in the cylinder, and to maintain the intake valve open during at least a later portion of the compression stroke to cycle the air and fuel charge into an intake manifold to mix the air and fuel charge; 
 code to maintain the at least one intake valve open from the compression stroke into an intake stroke to receive the mixed air and fuel charge from the intake manifold; and 
 code to transition the engine to HCCI combustion without applying spark ignition to the mixed air and fuel charge. 
 
     
     
       15. The medium of  claim 14 , wherein the HCCI combustion is a two-stroke HCCI combustion cycle. 
     
     
       16. The medium of  claim 14 , wherein if the engine is a direct injection engine, the medium comprising code to inject the fuel charge after an intake valve opening event. 
     
     
       17. The medium of  claim 14 , further comprising code to:
 retain some of the mixed air and fuel charge in the intake manifold; and 
 open the at least one intake valve to receive the mixed air and fuel charge from the intake manifold during the intake stroke following a first HCCI combustion. 
 
     
     
       18. The medium of  claim 15 , further comprising code to:
 retain some of the mixed air and fuel charge in the intake manifold; and 
 open the at least one intake valve to receive the mixed air and fuel charge from the intake manifold during the intake stroke following a second HCCI combustion.